Tzotzilthelphusa, Villalobos, José Luis & Álvarez, Fernando, 2013

Villalobos, José Luis & Álvarez, Fernando, 2013, Two new genera and three new species of freshwater crabs (Crustacea: Pseudothelphusidae: Potamocarcinini) from Chiapas, Mexico, Zootaxa 3599 (5), pp. 457-470 : 466

Tzotzilthelphusa n. gen.

Diagnosis. Carapace with dorsal surface convex, regions discernible, median groove narrow. Exopod of third maxilliped subequal in length to ischium. First male gonopod with distal third strongly bent laterally, compressed lateromesially, distal half slightly narrower, mesial margin widely curved. In mesial view, marginal suture straight along proximal two-thirds of gonopod, laterally bent on distal third ( Fig. 7 a). Marginal plate between caudal and mesial surfaces. Mesial process as triangular, stout, acute spine, cephalad directed, forming 90º angle with respect to principal axis of gonopod ( Fig. 7 a). Caudal surface straight, without medial notch. Lateral suture visible through almost entire length of gonopod. In cephalic view, distal portion of gonopod laterally directed, proximal two-thirds thicker, distal one compressed, separated from medial third by deep, wide, rounded constriction ( Fig. 7 b). Apical projection of mesial surface digitiform, with transverse rows of spines. In lateral view, gonopod of uniform thickness, surface punctated with scarce short setae, apical elements and apex cavity visible ( Fig. 7 c). Mesial surface of distal crest, thin, high, bordering inner surface of apical cavity. Distal crest of lateral surface blunt, cephalically reaching proximal half of mesial process, limiting apical cavity. Apical cavity narrow, elongated along a cephalo-caudal axis, limited cephalically by irregular laminar projection of lateral crest and caudally by marginal plate; opening of spermatic channel subcircular, in caudal position ( Fig. 7 c). In caudal view, distal portion of gonopod laterally directed, lateral suture visible along proximal two-thirds ( Fig. 7 d). Distal notch separating marginal plate from lateral surface obliterated. Distal end of marginal plate with acute spinules.

Type species. Tzotzilthelphusa villarosalensis n. sp.

Etymology. The generic name is derived from Tzotzil the name of the native people that inhabit this region of Chiapas and Thelphusa , the generic name for freshwater crabs.

Distribution. Known only from a small area south of the town of Teopisca in central Chiapas, Mexico.

Remarks. Based on the morphology of the male gonopod which does not show any torsion, although the distal third is inclined, Tzotzilthelphusa n. gen. is placed in the tribe Potamocarcinini. The new genus appears morphologically similar to Phrygiopilus in that the gonopods of both genera show a distal third inclined laterally, a laterally oriented apical cavity and a conical mesial process produced as a robust spine cephalically oriented at a 90º angle with respect to the longitudinal axis of the gonopod. The most important difference between Tzotzilthelphusa n. gen. and Phrygiopilus is the extent of development of the apical processes of the gonopod. In Phrygiopilus the supra-apical process is a large cap-like process developed on top of the apical cavity, while in Tzotzilthelphusa n. gen. the crest deriving from the mesial surface develops into a lobular projection with spinules. Phrygiopilus is also found in Chiapas, in the Montebello Lakes district with two species ( P. montebelloensis Álvarez & Villalobos, 1998 and P. yoshibensis Álvarez & Villalobos, 1998 ) and in northern Guatemala ( Álvarez & Villalobos, 1998).

In Tzotzilthelphusa n. gen. there is an incipient supra-apical process represented by the mesial surface that forms a structure that displaced the apical cavity to a oblique position with respect to the main axis of the gonopod, and develops beyond the marginal and mesial processes. The gonopod of Tzotzilthelphusa n. gen. is also similar to that of Typhlopseudothelphusa hyba Rodríguez & Hobbs, 1989 , a stygobitic species from Cueva de Los Llanos, near San Cristóbal de la Casas, Chiapas. These similarities are discussed below.

Figures

FIGURE 7. Tzotzilthelphusa villarosalensis n. sp., male holotype. Left first gonopod: a, mesial view; b, cephalic view; c, lateral view; d, caudal view. Abbreviations: ac, apex cavity; map, marginal process; mas, marginal suture; mep, mesial process; mes, mesial surface.